In the framework of the chiral quark model, we investigate the hidden strange pentaquark system of the $N\varphi$ state with quantum numbers of $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$. The results show that the $N\varphi$ state can be bound through the interaction of the $\sigma$ meson exchange plus the effect of channel coupling, which means that the effect of channel coupling has an influence on the existence of this bound state.

Background: Discrepancies exist between the observed abundances of argon and calcium in oxygen-neon nova ejecta and those predicted by nova models. An improved characterization of the ${}^{38}\mathrm{K}(p,\gamma ){}^{39}\mathrm{Ca}$ reaction rate over the nova temperature regime ($\sim 0.1–0.4$ GK), and thus the nuclear structure of ${}^{39}\mathrm{Ca}$ above the proton threshold [5770.92(63) keV], is necessary to resolve these contradictions.

Purpose: The present study was performed to search for low-spin proton resonances in the ${}^{38}\mathrm{K}+p$ system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in ${}^{39}\mathrm{Ca}$.

Methods: The level structure of ${}^{39}\mathrm{Ca}$ was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the ${}^{40}\mathrm{Ca}({}^3\mathrm{He},\alpha ){}^{39}\mathrm{Ca}$ reaction. Differential cross sections were measured over six laboratory angles at 21 MeV. Distorted-wave Born approximation calculations were performed to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the ${}^{38}\mathrm{K}(p,\gamma ){}^{39}\mathrm{Ca}$ reaction rate over the nova temperature regime.

Results: The resonance energies corresponding to two out of three astrophysically important states at 6154(5) and 6472.2(24) keV are measured with better precision than previous charged-particle spectroscopy measurements. A tentatively new state is discovered at 5908(3) keV. The spin-parity assignments of a few of the astrophysically important resonances are determined.

Conclusions: The present ${}^{38}\mathrm{K}(p,\gamma ){}^{39}\mathrm{Ca}$ upper limit thermonuclear reaction rate at 0.1–0.4 GK is higher than that determined by Christian et al. [Phys. Rev. C 97, 025802 (2018)] by at most a factor of 1.4 at 0.1 GK.

In this work, we study in detail the deconfinement phase transition that takes place in hot/dense nuclear matter in the context of neutron stars and proto-neutron stars (in which lepton fraction is fixed). The possibility of different mixtures of phases with different locally and globally conserved quantities is considered in each case. For this purpose, the chiral mean field model, an effective relativistic model that includes self-consistent chiral symmetry restoration and deconfinement to quark matter, is employed. Finally, we compare our results with blue results provided by perturbative QCD for different temperatures and conditions.

The nuclear response theory for isospin-transfer modes in the relativistic particle-vibration coupling framework is extended to include coupling of single nucleons to isospin-flip (charge-exchange) phonons in addition to the usual neutral vibrations. This new coupling introduces dynamical pion and $\rho$-meson exchange beyond the Hartree-Fock approximation up to infinite order. We investigate the impact of this new mechanism on the Gamow-Teller response of a few doubly magic neutron-rich nuclei, namely, ${}^{48}\mathrm{Ca},{}^{78}\mathrm{Ni},{}^{132}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$. It is found that the coupling to isospin-flip vibrations can have a non-negligible impact on the strength distribution and quenching of the giant resonance, globally improving the agreement with the experimental data. The corresponding $\beta$-decay half-lives of ${}^{78}\mathrm{Ni}$ and ${}^{132}\mathrm{Sn}$ are also calculated and found to be decreased by a factor of $\sim 2$ by the inclusion of the new phonons.

The ${}^6\mathrm{Be}$ continuum states were populated in the charge-exchange reaction ${}^1\mathrm{H}({}^6\mathrm{Li},{}^6\mathrm{Be})n$ collecting very high statistics data ($\sim 5\times {10}^6$ events) on the three-body $\alpha +p+p$ correlations. The ${}^6\mathrm{Be}$ excitation energy region below $\sim 3\mathrm{MeV}$ is considered, where the data are dominated by contributions from the $0^{+}$ and $2^{+}$ states. It is demonstrated how the high-statistics few-body correlation data can be used to extract detailed information on the reaction mechanism. Such a derivation is based on the fact that highly spin-aligned states are typically populated in the direct reactions.

Within the framework of the coalescence model based on the phase-space distributions of protons and neutrons generated from the iebe-vishnu hybrid model with ampt initial conditions, we study the spectra and elliptic flow of deuterons and helium-3 in relativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Larger Hadron Collider (LHC). Results from our model calculations for $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ at RHIC and Pb+Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ at the LHC are compared with available experimental data. Good agreements are generally seen between theoretical results and experimental data, except that the calculated yield of helium-3 in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ underestimates the data by about a factor of 2. Possible reasons for these discrepancies are discussed. We also make predictions on the spectra and elliptic flow of deuterons and helium-3 in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ that are being studied at LHC.

The astrophysical $S$ factor and reaction rate of the direct capture process $\alpha +d\to {}^6\mathrm{Li}+\gamma$, as well as the abundance of the ${}^6\mathrm{Li}$ element, are estimated in a three-body model. The initial state is factorized into the deuteron bound state and the $\alpha +d$ scattering state. The final nucleus ${}^6\mathrm{Li}$($1^{+}$) is described as a three-body bound state $\alpha +n+p$ in the hyperspherical Lagrange-mesh method. Corrections to the asymptotics of the overlap integral in the $S$ and $D$ waves have been done for the $E2 S$ factor. The isospin forbidden $E1 S$ factor is calculated from the initial isosinglet states to the small isotriplet components of the final ${}^6\mathrm{Li}$($1^{+}$) bound state. It is shown that the three-body model is able to reproduce the newest experimental data of the LUNA Collaboration for the astrophysical $S$ factor and the reaction rates within the experimental error bars. The estimated ${}^6\mathrm{Li}/\mathrm{H}$ abundance ratio of $(0.67\pm 0.01)\times {10}^{-14}$ is in a very good agreement with the recent measurement $(0.80\pm 0.18)\times {10}^{-14}$ of the LUNA Collaboration.

The lifetimes of the excited states belonging to the chiral-candidate doublet bands built on the $\pi h_{11/2}\otimes \nu h_{11/2}^{-1}$ configuration in ${}^{130}\mathrm{La}$ have been measured by applying the Doppler-shift attenuation method and the in-beam fast timing technique. Excited states were populated in the ${}^{121}\mathrm{Sb}({}^{12}\mathrm{C},3n)$ reaction at a bombarding energy of 54 MeV. The $7^{+}$ bandhead of the yrast band was identified as an isomeric state with a lifetime of $\tau \left(7^{+}\right)=0.38\left(7\right)\mathrm{ns}$. Similar reduced transition probabilities $B\left(M1\right)$ and $B\left(E2\right)$ were found for the states with the same spin in the partner bands. The results revealed an even-odd spin dependence in the $B\left(E2\right)$ values, whereas the $B\left(M1\right)$ values vary nearly monotonically with increasing spin. The experimental properties of the doublet bands in ${}^{130}\mathrm{La}$ are compared with theoretical calculations done in the frame of the two-quasiparticles-plus-triaxial-rotor model. The static chirality is not supported by the obtained data; however, chiral vibrations cannot be excluded.

Recent high-resolution nuclear resonance fluorescence experiments performed on the even-even Chromium isotopes ${}^{50,52,54}\mathrm{Cr}$ have lead to the identification (energy, spin, parity, and transition strength) of altogether 108 nuclear levels of spin $J=1$ (70 levels with $J^{\pi }=1^{-}$ and 38 with $J^{\pi }=1^{+}$) at excitation energies $E_x$ ranging roughly from 4.5 to 9.7 MeV. In this region just above the orbital magnetic-dipole scissors mode, sizable spin-flip magnetic-dipole strength as well as electric-dipole strength belonging to the pygmy dipole resonance (PDR) is expected. Using statistical measures for short- and long-range correlations, we perform an analysis of the fluctuation properties in the subspectra of the energy levels and also of the distributions of their respective dipole transition strengths. We compare the results with those of a random matrix ensemble interpolating between Poisson statistics generally describing the fluctuation properties in the energy spectra of many-body systems with collective, i.e., regular motion of the particles and the Gaussian orthogonal ensemble (GOE) for complex (i.e., chaotic) behavior. This comparison reveals that the spectral properties of the $1^{+}$ states are close to the GOE results while those of the $1^{-}$ states are closer to Poisson. This is confirmed by an analysis of the spectral fluctuations based on the method of Bayesian inference and corroborated by large-scale shell-model and quasiparticle-phonon model calculations, respectively. The nearly Poissonian behavior of the $1^{-}$ levels suggests a sizable collectivity of the PDR indeed.

Detailed information on isomeric states in $A\approx 135$ nuclei is exploited to benchmark shell-model calculations in the region northwest of doubly magic nucleus ${}^{132}\mathrm{Sn}$. The $N=79$ isotones ${}^{133}\mathrm{Xe}$ and ${}^{135}\mathrm{Ba}$ are studied after multinucleon transfer in the ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and in a pulsed-beam experiment at the FN tandem accelerator of the University of Cologne, Germany utilizing a ${}^9\mathrm{Be}+{}^{130}\mathrm{Te}$ fusion-evaporation reaction at a beam energy of 40 MeV. Isomeric states are identified via delayed $\gamma$-ray spectroscopy. Hitherto tentative excitation energy, spin, and parity assignments of the 2107-keV $J^{\pi }=23/2^{+}$ isomer in ${}^{133}\mathrm{Xe}$ are confirmed and a half-life of $T_{1/2}=8.64\left(13\right)$ ms is measured. The 2388-keV state in ${}^{135}\mathrm{Ba}$ is identified as a $J^{\pi }=23/2^{+}$ isomer with a half-life of 1.06(4) ms. The new results show a smooth onset of isomeric $J^{\pi }=23/2^{+}$ states along the $N=79$ isotones and close a gap in the high-spin systematics towards the recently investigated $J^{\pi }=23/2^{+}$ isomer in ${}^{139}\mathrm{Nd}$. The resulting systematics of $M2$ reduced transition probabilities is discussed within the framework of the nuclear shell model. Latest large-scale shell-model calculations employing the SN100PN, GCN50:82, SN100-KTH, and a realistic effective interaction reproduce the experimental findings generally well and give insight into the structure of the isomers.

The structures of yrast normal-deformed (ND) bands in Hf isotopes have been investigated using the unpaired cranked Nilsson-Strutinsky (CNS), and the paired cranked Nilsson-Strutinsky-Bogoliubov (CNSB) models. New optimized Nilsson parameters have been derived and used in the models to interpret the experimental data in ${}^{168–175}\mathrm{Hf}$ isotopes. The calculated kinematic moments of inertia, as well as the excitation energies of the yrast bands, have been compared with the experimental findings, and good agreements are observed. Configuration changes along the yrast lines have been traced by the aid of the CNS calculations. The calculated single-particle excitations shed more light on the nature of the crossings and successfully explain some features of the observed rotational bands which had not been clear before.

A study of photofission of ${}^{232}\mathrm{Th}$ and ${}^{238}\mathrm{U}$ was performed by using quasimonoenergetic, linearly polarized $\gamma$-ray beams from the High Intensity $\gamma$-ray Source at Triangle Universities Nuclear Laboratory. The prompt-photofission neutron polarization asymmetries, neutron multiplicities, and the photofission cross sections were measured in the near-barrier energy range of 4.3 to 6.0 MeV. This data set constitutes the lowest energy measurements of those observables to date using quasimonoenergetic photons. Large polarization asymmetries are observed in both nuclei, consistent with the $E1$ excitation as observed by another measurement of this kind made in a higher-energy range. Previous experimental evidence of a deep third minimum in the ${}^{238}\mathrm{U}$ fission barrier has been identified as an accelerator-induced background.

In this theoretical study, we establish an interrelationship between the nucleon-nucleon potential and the nuclear fusion reaction cross sections at low energies. The axially deformed self-consistent relativistic mean field with nonlinear $\mathrm{NL}{3}^{*}$ and TM1 force parameters is used to calculate the density distributions of the projectile and target nuclei, which are further used in the double-folding approach to obtain the nucleus-nucleus interaction potentials. The Wong formula is used to estimate the fusion cross section and barrier distributions from the nucleus-nucleus optical potential for Ni-based systems, which are known for fusion hindrance phenomena. The results of the application of the so-obtained nucleus-nucleus potential for the fusion cross section from the recently developed relativistic effective NN interactions (R3Y) are compared with the well-known, phenomenological M3Y potential. The effect of the nucleon-nucleon interaction potential on the fusion cross section, in terms of the nuclear interaction potential, is included in the present analysis. We found relatively good results from R3Y interactions below the barrier energies as compared to the M3Y potential concerning the experimental data.

Production of ${\pi }^0$ and $\eta$ mesons has been measured at midrapidity in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$. Measurements were performed in ${\pi }^0\left(\eta \right)\to \gamma \gamma$ decay channel in the $1\left(2\right)-20\text{GeV}/c$ transverse momentum range. A strong suppression is observed for ${\pi }^0$ and $\eta$ meson production at high transverse momentum in central $\mathrm{Cu}+\mathrm{Au}$ collisions relative to the $p+p$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to $\mathrm{Au}+\mathrm{Au}$ with comparable nuclear overlap. The $\eta /{\pi }^0$ ratio measured as a function of transverse momentum is consistent with $m_T$-scaling parametrization down to $p_T=2\mathrm{GeV}/c$, its asymptotic value is constant and consistent with $\mathrm{Au}+\mathrm{Au}$ and $p+p$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $e^{+}{e}^{-}$ collisions in a range of collision energies $\sqrt{s_{{}_{NN}}}=3-1800$ GeV. This suggests that the quark-gluon-plasma medium produced in $\mathrm{Cu}+\mathrm{Cu}$ collisions either does not affect the jet fragmentation into light mesons or it affects the ${\pi }^0$ and $\eta$ the same way.

The photoneutron cross sections of ${}^{162,163}\mathrm{Dy}$ have been measured for the first time in an energy region from the neutron threshold ($S_n$) up to $\approx 13\mathrm{MeV}$. The $(\gamma ,n)$ reaction was induced with quasimonochromatic laser Compton-scattered $\gamma$ rays, produced at the NewSUBARU laboratory. The corresponding $\gamma$-ray strength functions ($\gamma \mathrm{SF}$) have been calculated from the photoneutron cross sections. The data are compared to reanalyzed $\gamma \mathrm{SFs}$ of ${}^{160\text{–}164}\mathrm{Dy}$, which are measured below $S_n$. The excellent agreement with the photoneutron data at $S_n$ confirms the principle of detailed balance. Thus, a complete $\gamma \mathrm{SF}$ is established covering in total the energy region of $1\le E_{\gamma }\le 13$ MeV. These mid-shell well-deformed dysprosium isotopes all show scissors resonances with very similar structures. We find that our data predict the same integrated scissors strength as $(\gamma ,{\gamma }^{\prime })$ data when integrated over the same energy range, which shows that the scissors mode very likely is consistent with the generalized Brink hypothesis. Finally, using the $\gamma \mathrm{SFs}$ as input in the reaction code talys, we have deduced radiative neutron-capture cross sections and compared them to direct measurements. We find a very good agreement within the uncertainties, which gives further support to the experimentally determined $\gamma \mathrm{SFs}$.

We use a reference state based on symmetry-restored states from deformed mean-field or generator-coordinate-method (GCM) calculations in conjunction with the in-medium similarity-renormalization group (IMSRG) to compute spectra and matrix elements for neutrinoless double-beta ($0\nu \beta \beta$) decay. Because the decay involves ground states from two nuclei, we use evolved operators from the IMSRG in one nucleus in a subsequent GCM calculation in the other. We benchmark the resulting IMSRG+GCM method against complete shell-model diagonalization for both the energies of low-lying states in ${}^{48}\mathrm{Ca}$ and ${}^{48}\mathrm{Ti}$ and the $0\nu \beta \beta$ matrix element for the decay of ${}^{48}\mathrm{Ca}$, all in a single valence shell. Our approach produces better spectra than either the IMSRG with a spherical-mean-field reference or GCM calculations with unevolved operators. For the $0\nu \beta \beta$ matrix element the improvement is slight.

Isospin-relaxation times characterizing isospin transport processes between the projectile and the target with different $N/Z$ ratios and that between the neck and the spectator with different isospin asymmetries and densities in intermediate-energy heavy-ion collisions are studied within an isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model using the lattice Hamiltonian approach. The respective roles and timescales of the isospin diffusion and drift as the major mechanisms of isospin transport in intermediate-energy heavy-ion collisions are discussed. Effects of nuclear symmetry energy and neutron-proton effective mass splitting on the isospin relaxation times are examined.